Tight oil or gas formation fracturing process

ABSTRACT

According to the invention, a process of fracturing tight oil or gas formations by drilling a band of small holes into the oil or gas formation from a well borehole, so that more explosive or hydraulic fracturing fluids can be placed at a selected depth and positioned to provide more lifting and fracturing force on the oil or gas formation.

United States Patent 11 1 Driver 1 Oct. 1, 1974 [5 TIGHT OIL OR GASFORMATION 2,171,416 8/1939 Lee 166/307 FRACTURING PROCESS 2,271,0051/1942 Grebe 175/61 2,441,881 5/1948 H s 175 62 X Inventor: Driver, 19Sheridan 3,002,454 10/1961 ciizsnm 16 6/299 Arnold, Md 21212 3,285,33511 1966 Reistle, Jr. 166 271 x Q21 Filed km 8 1972 3,771,600 11/1973Hill 166/299 [21 Appl. N0.: 287,359 Primary Examiner stephen J. Novosad52 us. c1. 166/299, 175/61 [57] ABSTRACT [51] Int. Cl E21b 43/26, E21b7/08 According to the invention, a pr cess of fracturing 53 v w f Search1 299 30 307 271; tight oil or gas formations by drilling a band ofsmall 175/ 2 1 107; 102/21 23 holes into the oil or gas formation from awell borehole, so that more explosive or hydraulic fracturing 5References it d fluids can be placed at a selected depth and positionedUNITED STATES PATENTS to provide more lifting and fracturing force onthe oil 1,367,042 2/1921 Granville 175/62 x or gas formatlon' 1,786,17312/1930 Scharpenberg 175/107 3 Claims, 3 Drawing Figures Pmmmw H3.888.736

slim ear 5 PATENTEDUBI 11w 3.888.786

SHEETBBF 3 TIGHT OIL OR GAS FORMATION FRACTURING PROCESS BACKGROUND OFTHE INVENTION 1. Field of the Invention The invention relates to aprocess of fracturing tight oil or gas formations so that the oil or gasthat they contain can be produced.

2. Prior Art The permeability of an oil or gas formation is theresistance the formation has on the flow of oil or gas to a wellborehole. This resistance to flow is due to small and poorly connectedpore space in the formation. It has been an old practice in thepetroleum industry to fracture oil or gas formations by pumping fluidsunder high pressure into a well borehole, also the same thing isaccomplished by exploding explosive fluids in the well borehole. In bothcases the gas from the explosive fluids or the hydraulic fluids enterthe oil or gas formation through the exposed pore space in the wellborehole. The fracturing fluids entering the formation lifts theformation. This lifting of the formation causes cracks and enlarges porespace, in which oil or gas can flow with less resistance. In the UnitedStates there are millions of barrels of oil and a related amount of gasthat cannot be recovered because the formations can not be fractured asdescribed above. In these formations, fracturing fluids cannot enterbecause the pore space is too small and poorly connected. To createholes in the formation by shooting them with projectiles from a downhole gun has not been successful, because the projectiles cannotpenetrate deep enough due to the density of the formation. Theseformations are called tight oil or gas formations. A nuclear explosioncan fracture these formations, but the oil or gas formation has to havegreat vertical thickness for-nuclear fracturing to be feasible. In mostcases the tight formations are too thin in vertical thickness to usenuclear fracturing.

SUMMARY OF THE INVENTION An object of the invention is to provide aprocess for fracturing tight oil or gas formations by providing means ofaccumulating more fracturing fluids, exposing them to more pore spaceand placing them so they can provide more lifting force at a selecteddepth in an oil or gas formation than can be obtained from the wall of awell borehole at the same selected depth in an oil or gas formation.

A particular object of the invention is to drill a band consisting ofone or more layers, which consist of one or more small holes, into theoil or gas formation from a well borehole in the oil or gas formation.The holes that comprise a layer are drilled in the same plane atselected points around the circumference of the well borehole, and theyare drilled perpendicular to the well borehole into the oil or gasformation.

A further object of the invention is to inject the band of holes withliquid explosive, and ignite so the explosion can lift and fracture theoil or gas formation.

Another object of the invention is to inject the band of holes withfluids under high pressure so they can lift and fracture the oil or gasformation.

Another object of the invention is to drill several bands of holes atdifferent depths in one well borehole in an oil or gas formation thathas great vertical thickness. The bands of holes in the oil or gasformation would be injected with explosive liquid, and ignited eithersimultaneously or in sequence. Several bands with 40 foot holes drilledinto a formation with great vertical thickness could fracture theformation as well as the nuclear fracturing process presently beingused, without the damage to the formation, and without the danger ofunderground and above ground radiation pollution as would be present inthe case of nuclear fracturmg.

An object to the invention is to provide the process for drilling theholes into the oil or gas formation from a well borehole. This isaccomplished by lowering a string of tubing into the well borehole, thathas elbow attached at the downhole end of the tubing string. The stringof tubing is set so the open end of the 90 elbow is interfaced with thewell borehole wall where a hole is to be drilled. Then a drill bit islowered to the well borehole wall through the tubing string and 90elbow. The drill bit is attached by a tool joint to a flexible hollowshaft, that is slightly longer than the hole to be drilled. The flexiblehollow shaft is attached by a tool joint to a string of drill pipe thatextends up through the tubing string to the top of the well borehole.Machinery at the top of the well borehole turns the drill pipe string,which turns the flexible hollow shaft, which drills the drill bit intothe oil or gas formation. The flexible hollow shaft is used to turn anddrill the drill bit into the oil or gas formation by being able torotate and move through the ninety degree elbow. When the hole isdrilled to the desired depth, the machinery at the top of the wellborehole pulls the drill pipe string up until the flexible hollow shaftand drill bit are pulled from the hole and into the tubing string and 90elbow. Then the tubing string is rotated until the open end of theninety degree elbow interfaces the well borehole wall where the nexthole is to be drilled. A hole in the wall of the 90 elbow near its openend that interfaces with the well borehole wall, lets the drillingfluids that are pumped down through the drill pipe string, through theflexible hollow shaft, through the drill bit and with cuttings from thehole being drilled, be exhausted into the well borehole. Also, fordrilling deep oil or gas formations a downhole motor, with its inputattached to the drill pipe string and its output shaft attached to thetool joint attached to the flexible hollow shaft, rotates the flexiblehollow shaft and drill bit. This would be a slim motor, which could beinserted through the tubing string. The motor is used at deep depthsbecause slimdrill pipe being turned at the speed required to drill theformation at deep depths would probably part. The motor is operated bypumping drilling fluids down through the drill pipe string to the inputof the motor. The drilling fluids under pump pressure operate the motor.After the drilling fluids turn the motor they are exhausted through themotor output shaft into the flexible hollow shaft.

DESCRIPTION OF THE DRAWINGS In the accompanying drawings,

FIG. 1 is an overall view showing a band consisting of one layer ofsmall holes drilled in a tight oil or gas formationfrom a well borehole.

FIG. 2 is a cross section showing how the downhole tools system isconfigured to drill a small hole.

FIG. 3 is a cross section showing how a downhole motor would beincorporated into the downhole drilling system.

DESCRIPTION ()F THE PREFERRED EMBODIMENT Referring to the accompanyingdrawings which form a part of this disclosure a well borehole 2 drilledthrough tight oil or gas formation 1. At a selected depth in tight oilor gas formation 1, a band consisting of one layer consisting of severalsmall holes 4 are drilled into tight oil or gas formation 1 from thewall 3 of well borehole 2. The small hole 4 is drilled perpendicular towall 3 of well borehole 2 into tight oil or gas formation 2. After theband of small holes 4 has been drilled, they are pumped full of liquidexplosive and ignited, so the resulting explosion will lift and fracturetight oil or gas formation 1. The band of small holes 4 can also bepumped with fracturing fluids under high pressure to fracture tight oilor gas formation 1.

The small hole 4 is drilled into tight oil or gas formation 1 bylowering a tubing string into well borehole 2. The tubing string 5 has aninety degree elbow 6 attached to its downhole end. The tubing string 5is set in the well borehole 2, so that the open end 12 of ninety degreeelbow 6 will interface the wall 3 of the well borehole 2, where thesmall hole 4 is to be drilled. Then drill bit 7 is inserted down throughtubing string 5 and ninety degree elbow 6 to the wall 3 of well borehole2 where small hole 4 is to be drilled into tight oil or gas formation 1.The drill bit 7 is attached by a tool joint 8 to flexible hollow shaft9, which is slightly longer than the depth of the small hole 4 that isto be drilled. The flexible hollow shaft 9 is used because it is able torotate and move through ninety degree elbow 6 and drill drill bit 7 intothe tight oil or gas formation 1. The flexible hollow shaft 9 isattached by tool joint 10 to drill pipe string 11. The drill pipe string11 extends up through tubing string 5 to the top of well borehole 2.Machinery at the top of well borehole 2 rotates and applies downwarddrilling pressure on drill pipe string 1 1, which will drill drill bit 7and flexible hollow shaft 9 into tight oil or gas formation 1. To cleanthe cuttings from hole 4 while it is being drilled, drilling fluids arepumped down through drill pipe string 11, through flexible hollow shaft9 and through drill bit 7 into hole 4. The drilling fluids with cuttingsfrom hole 4 are exhausted into well borehole 2 through drain hole 13which is in the bottom of ninety degree elbow 6 near its open end 12which interfaces wall 3 of well borehole 2. When hole 4 has beendrilled, the machinery at the top of well borehole 2 pulls the drillstring 11 up until drill bit 7 and the flexible hollow shaft 9 arepulled from hole 4 and into tubing string 5 and 90 elbow 6. Then thetubing string 5 is rotated until the open end 12 of 90 elbow 6interfaces the point on wall 3 of well borehole 2 where the next hole 4is to be drilled.

At deep depths a downhole motor 14 is used to rotate flexible hollowshaft 9 and drill bit 7. The input of downhole motor 14 is attached tothe downhole end of drill pipe string 11, and the output shaft '15 ofdownhole motor 14 is attached to flexible hollow shaft 9 up tool joint10. Drilling fluids pumped down through drill pipe string 11 operatedownhole motor 14 and rotate its output shaft 15, which rotates flexiblehollow shaft 9 and drill bit 7. The drilling fluids are exhausted fromdownhole motor 14 through outputshaft 15 into flexible hollow shaft 9.The downhole motor 14 could be used at shallow depths.

Lclaim l. The process of fracturing tight oilor gasforma- I tions bydrilling into the the tight oil or gas formation from a selected depthin a well borehole in the tight oil or gas formation a band consistingof one or more layers which consist of small holes drilled perpendicularfrom the well borehole into the tight oil or gas formation, the smallholes which comprise a layer are drilled at the same depth and from asmany points that can be drilled around the circumference of the wellborehole so the small holes will radiate out from the well borehole intothe tight oil or gas formation, injecting liquid explosive into thesmall holes after they have been drilled and igniting said explosive toexert fracturing pressure on the tight oil or gas formation from thesmall holes, wherein the method used in drilling the small holesconsists of lowering a tubing string into the well borehole with aninety degree elbow attached to the downhole end of the tubing stringstring and setting the tubing string so the open end of the elbowinterfaces with the well borehole wall where a small hole is to bedrilled, lowering a drill pipe string down through the tubing stringwith a flexible hollow shaft attached to the downhole end of the drillpipe string, a tool joint attaching the uphole end of the flexiblehollow shaft to the downhole end of the drill pipe string and a drillbit attached to the downhole end of the flexible hollow shaft by meansof a tool joint, applying rotation and down pressure to the drill pipestring from the top of the well borehole whereby the drill pipe stringrotates and forces the drill bit and flexible hollow shaft through the90 elbow and drills the drill bit and flexible hollow shaft into thetight oil or gas formation drilling a small hole until the tool jointthat attaches the flexible hollow shaft to the drill pipe string is nearthe point where the tubing string attaches to the 90 elbow, thenapplying hoisting action to the drill pipe string by the conventionalwell drilling equipment at the top of the well borehole until theflexible hollow shaft and drill bit have been pulled from the drilledsmall hole in the tight oil or gas formation into the 90 elbow rotatingthe tubing string after the drill bit has been pulled into the 90 elbowuntil the open end of the 90 elbow interfaces with the well boreholewall where the next small hole of a layer is to be drilled, lowering thetubing string when all the small holes of a layer are drilled to thepoint in the well borehole where the next layer of small holes is to bedrilled if the band of small holes requires more than one layer of smallholes.

2. ln claim 1 comprising drilling one or more drain holes in the 90elbow near the ninety degree elbows open end which interfaces with thewell borehole wall so drilling fluids pumped down through the drill pipestring, through the tool joint that connects the drill pipe string tothe flexible hollow shaft, through the flexible hollow shaft, throughthe tool point that connects the flexible hollow shaft to the drill bit,through the drill bit into the small hole being drilled and withcuttings from the small hole being drilled can be exhausted into thewell borehole. M

3. In claim 1 when the tight oil or gas formation is at great depths orwhen very small holes are to be drilled a downhole motor attached to thedownhole end of the drill pipe string is used to rotate the flexiblehollow shaft and the drill bit, a tool joint attaches the uphole end ofthe flexible hollow shaft to the output shaft of the downhole motor.

1. The process of fracturing tight oil or gas formations by drillinginto the the tight oil or gas formation from a selected depth in a wellborehole in the tight oil or gas formation a band consisting of one ormore layers which consist of small holes drilled perpendicular from thewell borehole into the tight oil or gas formation, the small holes whichcomprise a layer are drilled at the same depth and from as many pointsthat can be drilled around the circumference of the well borehole so thesmall holes will radiate out from the well borehole into the tight oilor gas formation, injecting liquid explosive into the small holes afterthey have been drilled and igniting said explosive to exert fracturingpressure on the tight oil or gas forMation from the small holes, whereinthe method used in drilling the small holes consists of lowering atubing string into the well borehole with a ninety degree elbow attachedto the downhole end of the tubing string string and setting the tubingstring so the open end of the 90* elbow interfaces with the wellborehole wall where a small hole is to be drilled, lowering a drill pipestring down through the tubing string with a flexible hollow shaftattached to the downhole end of the drill pipe string, a tool jointattaching the uphole end of the flexible hollow shaft to the downholeend of the drill pipe string and a drill bit attached to the downholeend of the flexible hollow shaft by means of a tool joint, applyingrotation and down pressure to the drill pipe string from the top of thewell borehole whereby the drill pipe string rotates and forces the drillbit and flexible hollow shaft through the 90* elbow and drills the drillbit and flexible hollow shaft into the tight oil or gas formationdrilling a small hole until the tool joint that attaches the flexiblehollow shaft to the drill pipe string is near the point where the tubingstring attaches to the 90* elbow, then applying hoisting action to thedrill pipe string by the conventional well drilling equipment at the topof the well borehole until the flexible hollow shaft and drill bit havebeen pulled from the drilled small hole in the tight oil or gasformation into the 90* elbow rotating the tubing string after the drillbit has been pulled into the 90* elbow until the open end of the 90*elbow interfaces with the well borehole wall where the next small holeof a layer is to be drilled, lowering the tubing string when all thesmall holes of a layer are drilled to the point in the well boreholewhere the next layer of small holes is to be drilled if the band ofsmall holes requires more than one layer of small holes.
 2. In claim 1comprising drilling one or more drain holes in the 90* elbow near theninety degree elbows open end which interfaces with the well boreholewall so drilling fluids pumped down through the drill pipe string,through the tool joint that connects the drill pipe string to theflexible hollow shaft, through the flexible hollow shaft, through thetool point that connects the flexible hollow shaft to the drill bit,through the drill bit into the small hole being drilled and withcuttings from the small hole being drilled can be exhausted into thewell borehole.
 3. In claim 1 when the tight oil or gas formation is atgreat depths or when very small holes are to be drilled a downhole motorattached to the downhole end of the drill pipe string is used to rotatethe flexible hollow shaft and the drill bit, a tool joint attaches theuphole end of the flexible hollow shaft to the output shaft of thedownhole motor.